As shown in FIG. 1, in such as voice conversion technic (so-called voice changer) in which the tone of voice and tone color are changed by changing the frequency of a voice signal or a musical tone signal, digital signal processing technic is used in generally.
That is, the voice signal inputted from an input terminal 1 is converted into digital data by an analog/digital conversion circuit 2, and the digital voice signal temporarily stored in memory 3 is read out in a different sampling frequency, or is interpolated to read out, to a digital/analog conversion circuit 4, in which the data is converted again into an analog voice signal, under the control of a control unit 5 composed of microcomputer. Thereby, the voice signal different in frequency and amplitude from that of the input voice signal is outputted.
However, in this system, there is needed a digital signal processing circuit required such a higher technique that the analog/digital conversion circuit 2, the digital/analog conversion circuit 4 and memory 3 and the like are controlled by control unit composed of microcomputer 5, in order to achieve such only an effect that a tone and tone color can change. Therefore the system becomes more complex to obtain similar to the above effect.
Also, the conventional analog/digital and digital/analog conversion circuits 2 and 4 generate quantization noise in voice frequency band, so that the signal to noise ratio (S/N ratio) becomes greatly reduced. Therefore, when there is no signal, it is necessary to perform muting together with masking for the improvement of the S/N ratio for practical use.
Also, the peripheral devices may be subjected to electromagnetic disturbance, by the high frequency sampling clock signal.